purge gas recovery16th impca 2013 asian methanol conference john pach – johnson matthey purge gas...

John Pach – Johnson Matthey16th IMPCA 2013 Asian Methanol Conference

Purge gas recovery An attractive scheme for methanol-ammonia co-production

John Pach, John Brightling & Terry Fitzpatrick

Agenda

• Introduction• Methanol plant design

H d• Hydrogen recovery• Ammonia loop design• Advantages• Conclusion


Heysham, UK before 1960

Billingham 1970s – 2000s

Ammonia Plants

MethanolPlantsPSA

Hydrogen Loop Purge

Carbon Dioxide

Fuel


Co-production with ammonia loop

Ammonia Plants

MethanolPlantsPSA

Hydrogen Loop Purge

Carbon Dioxide

Ammonia Loop

FuelNitrogen

Agenda




Steam reforming

Fuel

Air

Steam

Steam

Feed

Syngas

CO2

SMR + ATR

Fuel Oxygen

Air

Steam

Steam

Feed

Syngas


Typical syngas compositions

Syngas technology R ratio CO/CO2 % CH4

SMR 2.9 2 3SMR+CO2 2.1 2 3SMR+ATR 2.1 3 1GHR+ATR 2.1 2 1Gasifier – coal1 2.05 10 0.5Gasifier - biomass 2.05 5 >5• R ratio – Excess H2 R = ([H2]-[CO2])/([CO]+[CO2])

• CO/CO2 – Heat of reaction/ reactivity

• CH4 – Loop efficiency1 Entrained flow gasifier

Methanol plant hydrogen balance

• Typical SMR with NG feed has 40% excess hydrogen• Hydrogen export• CO2 addition• ATR flowsheets• Fuel• Ammonia


Methanol plant hydrogen balance

• Typical SMR with NG feed has 40% excess hydrogen• Ammonia

O ti i d th l l t• Optimized methanol plant• High efficiency ammonia loop• Minimal cross connections/interactions

Hydrogen Recovery System

Scrubbed methanol loop purge

Hydrogen

Methanol Plant

Ammonia Loop

Scrubbed ammonia loop purge

Fuel

Agenda




Methanol purge gas treatment

• Need to remove• H2O

CO• CO• CO2

• Need to recover hydrogen• PSA• Nitrogen wash

• Need to add nitrogen

PSA

Nitrogen

Methanol Plant

PSA Unit

Ammonia Loop


Fuel

Scrubbed methanol loop purge Hydrogen


PSA

AdvantagesN i t

DisadvantagesH d f d 80 90%• No energy requirement

• No feed pre-treatment• Pure hydrogen• Stoichiometric nitrogen requirement

• Hydrogen recovery of order 80-90% so 10-20% is lost to fuel

• Can constrain loop operating pressure, if pressure let down is to be avoided.

Nitrogen

Methanol Plant

PSA Unit

Ammonia Loop


Fuel

Scrubbed methanol loop purge Hydrogen

Nitrogen wash

Nitrogen

Methanol Plant

Ammonia Loop


Fuel

Scrubbed methanol loop purge 3:1 H2:N2

Wet CO2removal

Nitrogen WashDrying


Nitrogen wash

AdvantagesH d 99% 10 20%

DisadvantagesAdditi l ifi ti t• Hydrogen recovery >99% 10-20%

more ammonia than with PSA• Operating pressure range

encompasses that of methanol synthesis loops

• Very pure stream of H2 and N2 in the ratio 3:1

• Additional purification steps• Much higher nitrogen requirement than

the PSA scheme larger ASU• Additional utility requirements• The waste gas stream contains the

excess nitrogen• Higher capital cost

Nitrogen

Methanol Plant

Ammonia Loop


Fuel

Scrubbed methanol loop purge 3:1 H2:N2

Wet CO2removal

Nitrogen WashDrying

Agenda




Ammonia synthesis

Ammonia loop design

• High efficiency loop• virtually inert free

Hi h k• High make-up gas pressure • Small syn gas compressor

• Steam for ammonia loop generated • After the ammonia converters• Fired heater

• Fuel gas from hydrogen recovery system. • Natural gas

• Ammonia steam system is independent of methanol steam system.

• Enhanced reliability


Agenda



Flexibility

• Whilst some co-production schemes lack the flexibility to adjust ammonia and methanol production to meet local market needs an ammonia loop is very flexiblemarket needs, an ammonia loop is very flexible • Increase ammonia production and reduce methanol

production • Send methanol plant syn gas to ammonia loop via HRU

• Reduce ammonia production for a fixed methanol production rate

• Use methanol purge gas as fuel. p g g• Change both ammonia and methanol rates

• Adjust flow through the reformer


Operating costs

Efficiency O & M costs• 30.2 GJ/te product

(7.2Gcal/te) • Hot Middle Eastern climate• Includes ASU• 1MWh = 10.8GJ

• For many plants• No increase in operating

and maintenance staff for over that required for stand alone methanol plant.

• Fewer pieces of equipment to maintainequipment to maintain• reduced turnaround cost.

Comparison with stand alone plants

Stand alone Co-production withPSA

Co-production withNitrogen Wash

Methanol plant Same Same Same

Primary reformer Yes No NoPrimary reformer Yes No No

Secondary Reformer Yes No No

Air compressor Yes No No

HTS & LTS Yes No No

Wet CO2 removal Yes No Much Smaller

Methanator Yes No No

SGD ? No Much smaller

SGC Yes Much smaller Much smallerSGC Yes Much smaller Much smaller

Ammonia loop Yes Much smaller Much smaller

Ammonia refrigeration Yes Smaller Smaller

ASU ? Yes Yes

HRU Small membrane PSA Nitrogen wash


Agenda



Conclusion

• Johnson Matthey and ThyssenKrupp Uhde offer state of the art designs for dedicated methanol plants, for dedicated ammonia plants and for an ammonia-methanoldedicated ammonia plants and for an ammonia methanol co-production scheme which does not compromise operability or reliability and which possesses excellent plant economics.

• We can assist operators to compare the viability of dedicated production assets with that of a co-production facility and provide whichever technology is the best fit forfacility and provide whichever technology is the best fit for any particular project.

purge gas recovery16th impca 2013 asian methanol conference john pach – johnson matthey purge gas...

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